The present invention relates to an image-taking apparatus such as a digital camera which takes images with a photoelectrical conversion element.
Known image-taking apparatuses as mentioned above include a digital camera of a single-lens reflex type which splits luminous flux for taking images through a quick return mirror into two, each for a viewfinder optical system and an image-pickup device (a photoelectrical conversion device). FIG. 5 shows an operational sequence of a conventional single-lens reflex digital camera.
In FIG. 5, when a release switch of the digital camera is pressed, a sequence motor is rotated while current is applied to a front curtain magnet and a rear curtain magnet of a shutter. The rotation of the sequence motor causes a quick return mirror to be moved upward and the mechanical lock of the shutter is released. Even after the mechanical lock of the shutter is released, a front curtain and a rear curtain of the shutter are held by the magnets.
When the sequence motor is rotated by a predetermined amount to complete the abovementioned operation, the sequence motor is stopped and an image-pickup device discharges unnecessary accumulated charge to start accumulating charge for taking images.
The quick return mirror bounds against a stopper at an up position (a position to which it is moved out of an image-taking optical path). To wait for the bound to stop, the current application to the front curtain magnet is stopped and the front curtain starts traveling after the elapse of a predetermined time period (time T77 in FIG. 5).
After the elapse of an exposure time set by an operator or automatically set by the camera from the start of the travel of the front curtain, the current application to the rear curtain is stopped and the rear curtain starts traveling. When the rear curtain completes the travel, the image-pickup device stops the accumulation of charge to start reading the charge.
After the reading of the charge is finished, the sequence motor is rotated again to perform preparatory driving for the next image-taking (driving for moving the mirror down and driving for shutter charge). When the driving for moving the mirror down is completed, luminous flux for taking images is directed to a photometric sensor and an AF sensor in the camera.
In recent cameras, image-pickup devices have higher resolution in order to take images with higher resolution. The higher resolution of the image-pickup device tends to increase the time taken for reading charge from the image-pickup device. The increased time for reading charge results in the problem of taking a longer time for one image-taking operation to reduce the speed in taking images.
As a solution for the problem, it is contemplated that preparatory driving for the next image-taking is started during charge reading (for example, see Japanese Patent Laid-Open No. 2000-50137). The preparatory driving for the next image-taking started during charge reading in the current image-taking operation can reduce the time taken for one image-taking operation.
When the preparatory driving for the next image-taking is started during charge reading, however, the starting current of a motor serving as a driving source for performing the preparatory driving sharply reduces the supply voltage. This leads to noise produced when the read charge is converted into voltage, which causes degraded image quality.
In conventional silver salt cameras, performing the preparatory driving for the next image-taking while a film is exposed to light of a subject image has been difficult in view of driving of a film transport system. In digital cameras, based on such convention, the preparatory driving for the next image-taking is typically performed after charge is read from an image-pickup device in an image-taking sequence.